Significant Accounting Policies (Details Textual) - USD ($)		12 Months Ended
	Mar. 31, 2014	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019
Significant Accounting Policies [Line Items]
Asset impairment charges		$ 0	$ 0	$ 0
Deferred revenue, revenue recognized		88,023,000
Sales returns		$ 0	$ 0	$ 0
Capitalized contract cost, amortization period (years)		4 years
Granted (in shares)		0	0	0
Stock-based compensation		$ 46,139,000	$ 34,961,000	$ 19,835,000
Gain on derivative		683,000	98,000
Severance and retirement costs		$ 6,390,000	$ 6,765,000	$ 4,801,000
Antidilutive securities excluded from computation of earnings per share, shares		3,033,718	3,173,188
Operating lease right-of-use asset		$ 55,057,000
Operating lease, liability, current		8,269,000
Operating lease liabilities long-term		57,040,000
Other Noncurrent Liabilities
Significant Accounting Policies [Line Items]
Restructuring reserve		$ 2,554,000	$ 2,391,000
United Kingdom | VSUK Plan
Significant Accounting Policies [Line Items]
Defined contribution plan, employer matching contribution, percent of match		100.00%
Defined contribution plan, employer matching contribution, percent of base pay		3.00%
Israel | VSUK Plan
Significant Accounting Policies [Line Items]
Defined contribution plan, maximum annual contributions per employee, percent		8.33%
Israel | VSIR Plan
Significant Accounting Policies [Line Items]
Defined contribution plan, employer matching contribution, percent of match		100.00%
Deferred Salary Arrangement | United States
Significant Accounting Policies [Line Items]
Defined contribution plan, employer matching contribution, percent of match		100.00%
Defined contribution plan, employer matching contribution, percent of participants contribution		50.00%
Foreign Exchange Contract
Significant Accounting Policies [Line Items]
Derivative, gain (loss) on derivative, net		$ 352,000	(3,741,000)
Derivative instruments, gain (loss) recognized in income		$ 0	$ 0
Accounting Standards Update 2016-02
Significant Accounting Policies [Line Items]
Deferred rent credit, current					$ (1,313,000)
Deferred rent credit, noncurrent					(4,236,000)
Operating lease right-of-use asset					53,274,000
Operating lease, liability, current					2,349,000
Operating lease liabilities long-term					$ 55,676,000
United States of America, Dollars
Significant Accounting Policies [Line Items]
Investment interest rate		1.71%
Minimum | Israel | VSIR Plan
Significant Accounting Policies [Line Items]
Defined contribution plan, employer matching contribution, percent of base pay		3.00%
Defined contribution plan, employer matching contribution, percent of participants contribution		3.00%
Minimum | Deferred Salary Arrangement | United States
Significant Accounting Policies [Line Items]
Defined contribution plan, contributions, percentage of participants base pay		3.00%
Minimum | United States of America, Dollars
Significant Accounting Policies [Line Items]
Investment interest rate			1.30%
Maximum | Israel | VSIR Plan
Significant Accounting Policies [Line Items]
Defined contribution plan, employer matching contribution, percent of base pay		5.00%
Defined contribution plan, employer matching contribution, percent of participants contribution		50.00%
Maximum | Netherlands | VNL Plan
Significant Accounting Policies [Line Items]
Defined contribution plan, employer matching contribution, percent of base pay		7.70%
Maximum | Deferred Salary Arrangement | United States
Significant Accounting Policies [Line Items]
Defined contribution plan, employer matching contribution, percent of base pay		3.00%
Defined contribution plan, contributions, percentage of participants base pay		5.00%
Participant matching contribution percentage of base remuneration		80.00%
Maximum | United States of America, Dollars
Significant Accounting Policies [Line Items]
Investment interest rate			2.77%
Short-term Deposits | US Treasury Securities | Maximum
Significant Accounting Policies [Line Items]
Short term investment maturity period		1 year	1 year
Maintenance and services
Significant Accounting Policies [Line Items]
Revenue, performance obligation, description of timing		one year
Promissory Note
Significant Accounting Policies [Line Items]
Maximum borrowing capacity	$ 7,000,000
Basis spread on variable rate	0.05%
Interest rate at period end		4.80%
Long-term line of credit		$ 0
Promissory Note | Minimum
Significant Accounting Policies [Line Items]
Debt instrument, interest rate, effective percentage	4.10%